Children with Attention Deficit-Hyperactivity Disorder (ADHD) routinely experience significant difficulties in many areas of their psychosocial functioning. When a secondary diagnosis of Oppositional Defiant Disorder (ODD) is also present, children with ADHD are at even greater risk for developing serious family conflict, affective disorders, and other complications. Given these differences, there is reason to question whether children with ADHD/ODD respond to treatment as do children with ADHD alone. To date, the research on ADHD parent training has not addressed the impact of this type of comorbidity. Nor has it systematically examined how treatment outcome may be affected by parent variables, such as parental distress. In response to this situation, this investigation proposes to evaluate the separate and joint impact of ODD and parental distress on ADHD parent training outcome within the same factorial design. Using a parent training program specifically designed for the ADHD population, the proposed study will involve 120 school-aged children, half of whom will carry a secondary ODD diagnosis. In addition to this ADHD versus ADHD/ODD distinction, subjects will be further subdivided as a function of high versus low parental distress. Multiple measures of child, parent, and family functioning will be collected at pretreatment, posttreatment, and during a 6 month follow-up assessment. It is expected that group differences will be found, with the ADHD/ODD-high parental stress group being the least responsive to parent training. The results from this study may then be used to establish a better fit between this form of treatment and the individual clinical management needs of children with ADHD and their parents. In addition, the obtained findings will provide insight as to what adjunctive procedures might need to be added to parent training to maximize its therapeutic impact.